Firewall Security Requirements Guide

U_Firewall_SRG_V1R2_Manual-xccdf.xml

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2018-09-13

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This Security Technical Implementation Guide is published as a tool to improve the security of Department of Defense (DoD) information systems. The requirements are derived from the National Institute of Standards and Technology (NIST) 800-53 and related documents. Comments or proposed revisions to this document should be sent via email to the following address: [email protected]

Vuln

Rule

Version

CCI

Severity

Title

Description

SV-94115r1_rule

SRG-NET-000019-FW-000003

CCI-001414

HIGH

The firewall must be configured to use filters that use packet headers and packet attributes, including source and destination IP addresses and ports, to prevent the flow of unauthorized or suspicious traffic between interconnected networks with different security policies (including perimeter firewalls and server VLANs).

Information flow control regulates where information is allowed to travel within a network and between interconnected networks. Blocking or restricting detected harmful or suspicious communications between interconnected networks enforces approved authorizations for controlling the flow of traffic.
The firewall that filters traffic outbound to interconnected networks with different security policies must be configured with filters (i.e., rules, access control lists [ACLs], screens, and policies) that permit, restrict, or block traffic based on organization-defined traffic authorizations. Filtering must include packet header and packet attribute information, such as IP addresses and port numbers.
Configure filters to perform certain actions when packets match specified attributes, including the following actions:
- Apply a policy
- Accept, reject, or discard the packets
- Classify the packets based on their source address
- Evaluate the next term in the filter
- Increment a packet counter
- Set the packets' loss priority
- Specify an IPsec SA (if IPsec is used in the implementation)
- Specify the forwarding path
- Write an alert or message to the system log

SV-94117r1_rule

SRG-NET-000235-FW-000160

CCI-001190

MEDIUM

The firewall must fail closed if the firewall filtering function is nonfunctional.

While failure to an open state may ensure users are not inconvenienced, it also circumvents a critical security network function that guards against direct and indirect network attacks. Allow traffic to flow without filtering or inspection puts the entire network and DoD critical assets at immediate risk. An example is a network element that blocks all traffic rather than allowing all traffic when a network element component fails (e.g., fail closed and do not forward traffic). This prevents an attacker from forcing a failure of the system in order to obtain access.

SV-94119r1_rule

SRG-NET-000362-FW-000028

CCI-002385

HIGH

The firewall must employ filters that prevent or limit the effects of all types of commonly known denial-of-service (DoS) attacks, including flooding, packet sweeps, and unauthorized port scanning.

Not configuring a key boundary security protection device such as the firewall against commonly known attacks is an immediate threat to the protected enclave because they are easily implemented by those with little skill. Directions for the attack are obtainable on the Internet and in hacker groups. Without filtering enabled for these attacks, the firewall will allow these attacks beyond the protected boundary.
Configure the perimeter and internal boundary firewall to guard against the three general methods of well-known DoS attacks: flooding attacks, protocol sweeping attacks, and unauthorized port scanning.
Flood attacks occur when the host receives too much traffic to buffer and slows down or crashes. Popular flood attacks include ICMP flood and SYN flood. A TCP flood attack of SYN packets initiating connection requests can overwhelm the device until it can no longer process legitimate connection requests, resulting in denial of service. An ICMP flood can overload the device with so many echo requests (ping requests) that it expends all its resources responding and can no longer process valid network traffic, also resulting in denial of service. An attacker might use session table floods and SYN-ACK-ACK proxy floods to fill up the session table of a host.
In an IP address sweep attack, an attacker sends ICMP echo requests (pings) to multiple destination addresses. If a target host replies, the reply reveals the target's IP address to the attacker. In a TCP sweep attack, an attacker sends TCP SYN packets to the target device as part of the TCP handshake. If the device responds to those packets, the attacker gets an indication that a port in the target device is open, which makes the port vulnerable to attack. In a UDP sweep attack, an attacker sends UDP packets to the target device. If the device responds to those packets, the attacker gets an indication that a port in the target device is open, which makes the port vulnerable to attack.
In a port scanning attack, an unauthorized application is used to scan the host devices for available services and open ports for subsequent use in an attack. This type of scanning can be used as a DoS attack when the probing packets are sent excessively.

SV-94121r1_rule

SRG-NET-000202-FW-000039

CCI-001109

HIGH

The firewall must be configured to use filters that prevent or limit the effects of all types of commonly known denial-of-service (DoS) attacks, including flooding, packet sweeps, and unauthorized port scanning.

To prevent malicious or accidental leakage of traffic, organizations must implement a deny-by-default security posture at the network perimeter. Such rulesets prevent many malicious exploits or accidental leakage by restricting the traffic to only known sources and only those ports, protocols, or services that are permitted and operationally necessary.
As a managed boundary interface, the firewall must block all inbound and outbound network traffic unless a filter is installed to explicitly allow it. The allow filters must comply with the Ports, Protocols, and Services Management (PPSM) Category Assurance List (CAL) and Vulnerability Assessment (VA).

SV-94123r1_rule

SRG-NET-000132-FW-000026

CCI-000382

MEDIUM

The firewall must be configured to prohibit or restrict the use of functions, ports, protocols, and/or services on the network segment in accordance as defined in the Ports, Protocols, and Services Management (PPSM) CAL and vulnerability assessments.

Some ports, protocols, or services have well-known exploits or security weaknesses that can be leveraged in an attack against the enclave and put it at immediate risk. These ports, protocols, and services must be prohibited or restricted in the packet or stateful filtering firewall configuration in accordance with DoD policy.
Policy filters restrict traffic destined to the enclave perimeter as defined in the PPSM CAL and vulnerability assessments.

SV-94125r1_rule

SRG-NET-000192-FW-000029

CCI-001094

MEDIUM

The firewall must block outbound traffic containing denial-of-service (DoS) attacks to protect against the use of internal information systems to launch any DoS attacks against other networks or endpoints.

DoS attacks can take multiple forms but have the common objective of overloading or blocking a network or host to deny or seriously degrade performance. If the network does not provide safeguards against DoS attacks, network resources will be unavailable to users.
Installation of a firewall at key boundaries in the architecture mitigates the risk of DoS attacks. These attacks can be detected by matching observed communications traffic with patterns of known attacks and monitoring for anomalies in traffic volume/type.
The firewall must include protection against DoS attacks that originate from inside the enclave that can affect either internal or external systems. These attacks may use legitimate or rogue endpoints from inside the enclave. These attacks can be simple "floods" of traffic to saturate circuits or devices, malware that consumes CPU and memory on a device or causes it to crash, or a configuration issue that disables or impairs the proper function of a device. For example, an accidental or deliberate misconfiguration of a routing table can misdirect traffic for multiple networks.

SV-94127r1_rule

SRG-NET-000193-FW-000030

CCI-001095

MEDIUM

The firewall implementation must manage excess bandwidth to limit the effects of packet flooding types of denial-of-service (DoS) attacks.

A firewall experiencing a DoS attack will not be able to handle production traffic load. The high utilization and CPU caused by a DoS attack will also have an effect on control keep-alives and timers used for neighbor peering resulting in route flapping and will eventually black hole production traffic.
The device must be configured to contain and limit a DoS attack's effect on the device's resource utilization. The use of redundant components and load balancing are examples of mitigating "flood-type" DoS attacks through increased capacity.

SV-94129r1_rule

SRG-NET-000061-FW-000001

CCI-000067

MEDIUM

The firewall that filters traffic from the VPN access points must be configured with organization-defined filtering rules that apply to the monitoring of remote access traffic.

The firewall must generate traffic log records when traffic is denied, restricted, or discarded.

Without generating log records that log usage of objects by subjects and other objects, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.
Security objects are data objects that are controlled by security policy and bound to security attributes.
The firewall must not forward traffic unless it is explicitly permitted via security policy. Logging for firewall security-related sources such as screens and security policies must be configured separately. To ensure security objects such as firewall filters (i.e., rules, access control lists [ACLs], screens, and policies) send events to a syslog server and local logs, security logging must be configured one each firewall term.

SV-94137r1_rule

SRG-NET-000493-FW-000007

CCI-000172

MEDIUM

The firewall must generate traffic log records when attempts are made to send packets between security zones that are not authorized to communicate.

Without generating log records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.
Access for different security levels maintains separation between resources (particularly stored data) of different security domains.
The firewall can be configured to use security zones that are configured with different security policies based on risk and trust levels. These zones can be leveraged to prevent traffic from one zone from sending packets to another zone. For example, information from certain IP sources will be rejected if the destination matches specified security zones that are not authorized.

SV-94139r1_rule

SRG-NET-000399-FW-000008

CCI-001462

MEDIUM

The firewall must be configured to allow authorized users to record a packet capture based IP, traffic type (TCP, UDP, or ICMP), or protocol.

Without the ability to capture, record, and log content related to a user session, investigations into suspicious user activity would be hampered.
This configuration ensures the ability to select specific sessions to capture in order to support general auditing/incident investigation or to validate suspected misuse.

SV-94141r1_rule

SRG-NET-000074-FW-000009

CCI-000130

MEDIUM

The firewall must generate traffic log entries containing information to establish what type of events occurred.

Without establishing what type of event occurred, it would be difficult to establish, correlate, and investigate the events leading up to an outage or attack.
Audit event content that may be necessary to satisfy this requirement includes, for example, time stamps, source and destination addresses, user/process identifiers, event descriptions, success/fail indications, filenames involved, and access control or flow control rules invoked.
Associating event types with detected events in the network element logs provides a means of investigating an attack, recognizing resource utilization or capacity thresholds, or identifying an improperly configured network element.

SV-94143r1_rule

SRG-NET-000075-FW-000010

CCI-000131

MEDIUM

The firewall must generate traffic log entries containing information to establish when (date and time) the events occurred.

Without establishing when events occurred, it is impossible to establish, correlate, and investigate the events leading up to an outage or attack.
In order to compile an accurate risk assessment, and provide forensic analysis of network traffic patterns, it is essential for security personnel to know when flow control events occurred (date and time) within the infrastructure.
Associating event types with detected events in the network traffic logs provides a means of investigating an attack, recognizing resource utilization or capacity thresholds, or identifying an improperly configured network element.

SV-94145r1_rule

SRG-NET-000076-FW-000011

CCI-000132

MEDIUM

The firewall must generate traffic log entries containing information to establish the location on the network where the events occurred.

Without establishing where events occurred, it is impossible to establish, correlate, and investigate the events leading up to an outage or attack.
In order to compile an accurate risk assessment and provide forensic analysis, it is essential for security personnel to know where events occurred, such as network element components, modules, device identifiers, node names, and functionality.
Associating information about where the event occurred within the network provides a means of investigating an attack, recognizing resource utilization or capacity thresholds, or identifying an improperly configured network element.

SV-94147r1_rule

SRG-NET-000077-FW-000012

CCI-000133

LOW

The firewall must generate traffic log entries containing information to establish the source of the events, such as the source IP address at a minimum.

Without establishing the source of the event, it is impossible to establish, correlate, and investigate the events leading up to an outage or attack. In order to compile an accurate risk assessment and provide forensic analysis, security personnel need to know the source of the event.
In addition to logging where events occur within the network, the traffic log events must also identify sources of events, such as IP addresses, processes, and node or device names.

SV-94149r1_rule

SRG-NET-000078-FW-000013

CCI-000134

MEDIUM

The firewall must generate traffic log entries containing information to establish the outcome of the events, such as, at a minimum, the success or failure of the application of the firewall rule.

Without information about the outcome of events, security personnel cannot make an accurate assessment as to whether an attack was successful or if changes were made to the security state of the network.
Event outcomes can include indicators of event success or failure and event-specific results. They also provide a means to measure the impact of an event and help authorized personnel to determine the appropriate response.

SV-94151r1_rule

SRG-NET-000333-FW-000014

CCI-001844

MEDIUM

The firewall must be configured to send traffic log entries to a central audit server for management and configuration of the traffic log entries.

Without the ability to centrally manage the content captured in the traffic log entries, identification, troubleshooting, and correlation of suspicious behavior would be difficult and could lead to a delayed or incomplete analysis of an ongoing attack.
The DoD requires centralized management of all network component audit record content. Network components requiring centralized traffic log management must have the ability to support centralized management. The content captured in traffic log entries must be managed from a central location (necessitating automation). Centralized management of traffic log records and logs provides for efficiency in maintenance and management of records, as well as the backup and archiving of those records.
Ensure at least one syslog server is configured on the firewall.
If the product inherently has the ability to store log records locally, the local log must also be secured. However, this requirement is not met since it calls for a use of a central audit server.

SV-94153r1_rule

SRG-NET-000335-FW-000017

CCI-001858

MEDIUM

If communication with the central audit server is lost, the firewall must generate a real-time alert to, at a minimum, the SCA and ISSO.

Without a real-time alert (less than a second), security personnel may be unaware of an impending failure of the audit functions and system operation may be adversely impacted. Alerts provide organizations with urgent messages. Automated alerts can be conveyed in a variety of ways, including via a regularly monitored console, telephonically, via electronic mail, via text message, or via websites.
Log processing failures include software/hardware errors, failures in the log capturing mechanisms, and log storage capacity being reached or exceeded. Most firewalls use UDP to send audit records to the server and cannot tell if the server has received the transmission, thus the site should either implement a connection-oriented communications solution (e.g., TCP) or implement a heartbeat with the central audit server and send an alert if it is unreachable.

SV-94155r1_rule

SRG-NET-000088-FW-000018

CCI-000139

MEDIUM

The firewall must be configured to send a real-time alert to the ISSO and SA (at a minimum) in the event of an audit processing failure on the firewall itself.

It is critical for the appropriate personnel to be aware if a system is at risk of failing to process traffic logs as required. Without this notification, the security personnel may be unaware of an impending failure of the audit capability and system operation may be adversely affected.
Audit processing failures include software/hardware errors, failures in the audit capturing mechanisms, and audit storage capacity being reached or exceeded. Most firewalls use User Datagram Protocol (UDP) to send audit records to the server and cannot tell if the server has received the transmission. Thus, when the event daemon stops working, messages and notifications cannot be sent to the event monitor (e.g., Network Management System [NMS], Security Information and Event Management [SIEM], Syslog) or to the Simple Network Management Protocol (SNMP) server. Another method such as a keep-alive with the central audit server may be required.
This requirement applies to each audit data storage repository (i.e., distinct information system component where traffic log records are stored), the centralized audit storage capacity of organizations (i.e., all audit data storage repositories combined), or both.
Note that CCI-001858 requires that audit failure alerts be in real time; thus, simply sending a log event to the central audit server is not sufficient.

SV-94157r1_rule

SRG-NET-000089-FW-000019

CCI-000140

MEDIUM

In the event that communication with the central audit server is lost, the firewall must continue to queue traffic log records locally.

It is critical that when the network element is at risk of failing to process traffic logs as required, it takes action to mitigate the failure. Audit processing failures include software/hardware errors, failures in the audit capturing mechanisms, and audit storage capacity being reached or exceeded. Responses to audit failure depend on the nature of the failure mode.
In accordance with DoD policy, the traffic log must be sent to a central audit server. When logging functions are lost, system processing cannot be shut down because firewall availability is an overriding concern given the role of the firewall in the enterprise. The system should either be configured to log events to an alternative server or queue log records locally. Upon restoration of the connection to the central audit server, action should be taken to synchronize the local log data with the central audit server.
If the central audit server uses User Datagram Protocol (UDP) communications instead of a connection oriented protocol such as TCP, a method for detecting a lost connection must be implemented.

SV-94159r1_rule

SRG-NET-000098-FW-000021

CCI-000162

MEDIUM

The firewall must protect traffic log records from unauthorized access while in transit to the central audit server.

Auditing and logging are key components of any security architecture. Logging the actions of specific events provides a means to investigate an attack, recognize resource utilization or capacity thresholds, or identify an improperly configured firewall. Thus, it is imperative that the collected log data be secured and access be restricted to authorized personnel. Methods of protection may include encryption or logical separation.
This does not apply to traffic logs generated on behalf of the device itself (management). Some devices store traffic logs separately from the system logs.

Auditing and logging are key components of any security architecture. Logging the actions of specific events provides a means to investigate an attack, recognize resource utilization or capacity thresholds, or identify an improperly configured firewall. Thus, it is imperative that the collected log data be secured and can only be accessed by authorized personnel.
This does not apply to traffic logs generated on behalf of the device itself (management). Some devices store traffic logs separately from the system logs.

SV-94163r1_rule

SRG-NET-000099-FW-000161

CCI-000163

MEDIUM

The firewall must protect the traffic log from unauthorized modification of local log records.

If audit data were to become compromised, forensic analysis and discovery of the true source of potentially malicious system activity would be impossible to achieve.
To ensure the veracity of audit data, the information system and/or the application must protect audit information from unauthorized modification. This can be achieved through multiple methods, which will depend on system architecture and design. Some commonly employed methods include ensuring log files receive the proper file system permissions and limiting log data locations.
Audit information includes all information (e.g., audit records, audit settings, and audit reports) needed to successfully audit information system activity.
This does not apply to traffic logs generated on behalf of the device itself (management).

SV-94165r1_rule

SRG-NET-000100-FW-000023

CCI-000164

MEDIUM

The firewall must protect the traffic log from unauthorized deletion of local log files and log records.

If audit data were to become compromised, forensic analysis and discovery of the true source of potentially malicious system activity would be impossible to achieve.
To ensure the veracity of audit data, the information system and/or the application must protect audit information from unauthorized modification. This can be achieved through multiple methods, which will depend on system architecture and design. Some commonly employed methods include ensuring log files receive the proper file system permissions and limiting log data locations.
Audit information includes all information (e.g., audit records, audit settings, and audit reports) needed to successfully audit information system activity.
This requirement does not apply to traffic logs generated on behalf of the device itself (device management).

SV-94167r1_rule

SRG-NET-000131-FW-000025

CCI-000381

MEDIUM

The firewall must disable or remove unnecessary network services and functions that are not used as part of its role in the architecture.

Network devices are capable of providing a wide variety of functions (capabilities or processes) and services. Some of these functions and services are installed and enabled by default. The organization must determine which functions and services are required to perform the content filtering and other necessary core functionality for each component of the firewall. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors.
Some services may be security related but, based on the firewall's role in the architecture, must not be installed on the same hardware. For example, the device may serve as a router, VPN, or other perimeter services. However, if these functions are not part of the documented role of the firewall in the enterprise or branch architecture, the software and licenses should not be installed on the device. This mitigates the risk of exploitation of unconfigured services or services that are not kept updated with security fixes. If left unsecured, these services may provide a threat vector.
Some services are not authorized for combination with the firewall and individual policy must be in place to instruct the administrator to remove these services. Examples of these services are Network Time Protocol (NTP), domain name server (DNS), email server, FTP server, web server, and Dynamic Host Configuration Protocol (DHCP).
Only remove unauthorized services. This control is not intended to restrict the use of firewalls with multiple authorized roles.

SV-94169r1_rule

SRG-NET-000235-FW-000133

CCI-001190

MEDIUM

The firewall must fail to a secure state if the firewall filtering functions fail unexpectedly.

Firewalls that fail suddenly and with no incorporated failure state planning may leave the hosting system available but with a reduced security protection. Failure to a known safe state helps prevent systems from failing to a state that may cause unauthorized access to make changes to the firewall filtering functions.
This applies to the configuration of the gateway or network traffic security function of the device. Abort refers to stopping the firewall filtering function before it has finished naturally. The term abort refers to both requested and unexpected terminations.

SV-94171r1_rule

SRG-NET-000236-FW-000027

CCI-001665

MEDIUM

In the event of a system failure of the firewall function, the firewall must be configured to save diagnostic information, log system messages, and load the most current security policies, rules, and signatures when restarted.

Failure to a secure state can address safety or security in accordance with the mission needs of the organization. Failure to a secure state helps prevent a loss of confidentiality, integrity, or availability in the event of a failure of the information system or a component of the system. Preserving state information helps to facilitate the restart of the firewall application and a return to the operational mode with less disruption.
This requirement applies to a failure of the firewall function rather than the device or operating system as a whole, which is addressed in the Network Device Management SRG.
Since it is usually not possible to test this functionality in a production environment, systems should be validated either in a testing environment or prior to installation. This requirement is usually a function of the design of the firewall. Compliance can be verified by acceptance/validation processes or vendor attestation.

SV-94173r1_rule

SRG-NET-000362-FW-000159

CCI-002385

MEDIUM

The perimeter firewall must be configured for service redundancy, load balancing, or other organization-defined safeguards to limit the effects of types of denial-of-service (DoS) attacks on the network.

As a critical security system, perimeter firewalls must be safeguarded with redundancy measures. If the network does not provide safeguards against DoS attacks, network resources will be unavailable to users. Service redundancy techniques reduce the susceptibility of the firewall to many DoS attacks.
A firewall experiencing a DoS attack will not be able to handle the traffic load. The high CPU utilization caused by a DoS attack will also have impact control keep-alives and timers used for neighbor peering, resulting in route flapping and eventually black hole traffic.
Though redundant hardware is the primary means of compliance, there are a number of ways to meet this requirement. The firewall can also be configured for filter-based forwarding, per-flow load balancing, and/or per-packet load balancing.

SV-94175r1_rule

SRG-NET-000364-FW-000031

CCI-002403

MEDIUM

The firewall must apply ingress filters to traffic that is inbound to the network through any active external interface.

Unrestricted traffic to the trusted networks may contain malicious traffic that poses a threat to an enclave or to other connected networks. Additionally, unrestricted traffic may transit a network, which uses bandwidth and other resources.
Firewall filters control the flow of network traffic, ensure the flow of traffic is only allowed from authorized sources to authorized destinations. Networks with different levels of trust (e.g., the Internet) must be kept separated.

SV-94177r2_rule

SRG-NET-000364-FW-000032

CCI-002403

MEDIUM

The firewall must apply egress filters to traffic that is outbound from the network through any internal interface.

If outbound communications traffic is not filtered, hostile activity intended to harm other networks or packets from networks destined to unauthorized networks may not be detected and prevented.
Access control policies and access control lists implemented on devices, such as firewalls, that control the flow of network traffic ensure the flow of traffic is only allowed from authorized sources to authorized destinations. Networks with different levels of trust (e.g., the Internet) must be kept separated.
This requirement addresses the binding of the egress filter to the interface/zone rather than the content of the egress filter.

SV-94179r1_rule

SRG-NET-000364-FW-000033

CCI-002403

MEDIUM

The firewall must establish ingress filters that block inbound packets where the destination is an IP address assigned to the management or loopback addresses of the enclave protection devices unless the packet has a source address assigned to the management network or network infrastructure.

The firewall must reject requests for access or services where the source address received by the firewall specifies a loopback address. The loopback address is used by an Inter-Processor Control (IPC) mechanism that enables the client and server portion of an application running on the same machine to communicate, and so it is trusted. It should never be used as the source IP address of an inbound or outbound transmission.
It is a best practice for the management network to use the loopback addresses.

SV-94181r1_rule

SRG-NET-000364-FW-000034

CCI-002403

MEDIUM

The firewall must block or restrict inbound IP packets destined to the control plane of the firewall itself.

As a critical security system, perimeter firewalls must be safeguarded against direct attacks to the device. The firewall must have a filter that rejects requests for access or services where the source address received by the firewall specifies an external address and the destination address specifies the control plane of the firewall.

The management network must still have its own subnet in order to enforce control and access boundaries provided by Layer 3 network nodes such as routers and firewalls. Management traffic between the managed network elements and the management network is routed via the same links and nodes as that used for production or operational traffic.
Safeguards must be implemented to ensure that the management traffic does not leak past the managed network's premise equipment. If a firewall is located behind the premise router, all management traffic must be blocked at that point, with the exception of management traffic destined to premise equipment.

SV-94185r1_rule

SRG-NET-000364-FW-000036

CCI-002403

MEDIUM

The firewall must restrict traffic entering the VPN tunnels to the management network to only the authorized management packets based on destination address.

Protect the management network with a filtering firewall configured to block unauthorized traffic. This requirement is similar to the out-of-band management (OOBM) model, when the production network is managed in-band. The management network could also be housed at a Network Operations Center (NOC) that is located locally or remotely at a single or multiple interconnected sites.
NOC interconnectivity, as well as connectivity between the NOC and the managed networks' premise routers, would be enabled using either provisioned circuits or VPN technologies such as IPsec tunnels or MPLS VPN services.

If outbound communications traffic is not filtered, hostile activity intended to harm other networks may not be detected and prevented.

SV-94189r1_rule

SRG-NET-000365-FW-000038

CCI-001126

MEDIUM

The firewall must be configured to fail securely in the event of an operational failure of the firewall filtering or boundary protection function.

If a boundary protection device fails in an unsecure manner (open), information external to the boundary protection device may enter, or the device may permit unauthorized information release.
Secure failure ensures that when a boundary control device fails, all traffic will be subsequently denied.
Fail secure is a condition achieved by employing information system mechanisms to ensure that in the event of operational failures of boundary protection devices at managed interfaces (e.g., routers, firewalls, guards, and application gateways residing on protected subnetworks commonly referred to as demilitarized zones), information systems do not enter into unsecure states where intended security properties no longer hold.

SV-94191r1_rule

SRG-NET-000205-FW-000040

CCI-001097

MEDIUM

The perimeter firewall must filter traffic destined to the internal enclave in accordance with the specific traffic that is approved and registered in the Ports, Protocols, and Services Management (PPSM) Category Assurance List (CAL), Vulnerability Assessments (VAs) for that the enclave.

The enclave's internal network contains the servers where mission-critical data and applications reside. Malicious traffic can enter from an external boundary or originate from a compromised host internally.
Vulnerability assessments must be reviewed by the SA and protocols must be approved by the IA staff before entering the enclave.
Firewall filters (e.g., rules, access control lists [ACLs], screens, and policies) are the first line of defense in a layered security approach. They permit authorized packets and deny unauthorized packets based on port or service type. They enhance the posture of the network by not allowing packets to even reach a potential target within the security domain. The filters provided are highly susceptible ports and services that should be blocked or limited as much as possible without adversely affecting customer requirements. Auditing packets attempting to penetrate the network but stopped by the firewall filters will allow network administrators to broaden their protective ring and more tightly define the scope of operation.
If the perimeter is in a Deny-by-Default posture and what is allowed through the filter is in accordance with the PPSM CAL and VAs for the enclave, and if the permit rule is explicitly defined with explicit ports and protocols allowed, then all requirements related to the database being blocked would be satisfied.

SV-94193r1_rule

SRG-NET-000113-FW-000005

CCI-000169

LOW

The firewall must be configured to allow the system administrator to select a subset of DoD-required auditable events.

The generation of logs with a subset of criteria aide the system administrator, maintainers, and auditors when troubleshooting issues or reviewing the log for trends or security breaches.
Traffic log records can be generated from various components within the information system (e.g., network interface, access control list, or filter).
The DoD list of auditable events include the logging and audit requirements required by this document and any additional local requirements.

SV-94195r1_rule

SRG-NET-000392-FW-000042

CCI-002664

LOW

The firewall must generate an alert that can be forwarded to, at a minimum, the ISSO and ISSM when denial-of-service (DoS) incidents are detected.

Without an alert, security personnel may be unaware of major detection incidents that require immediate action, and this delay may result in the loss or compromise of information.
The firewall generates an alert that notifies designated personnel of the Indicators of Compromise (IOCs), which require real-time alerts. These messages should include a severity level indicator or code as an indicator of the criticality of the incident. These indicators reflect the occurrence of a compromise or a potential compromise.
Since these incidents require immediate action, these messages are assigned a critical or level 1 priority/severity, depending on the system's priority schema.
CJCSM 6510.01B, "Cyber Incident Handling Program", lists nine Cyber Incident and Reportable Event Categories. DoD has determined that categories identified by CJCSM 6510.01B Major Indicators (category 1, 2, 4, or 7 detection events) will require an alert when an event is detected.
Alerts may be transmitted, for example, telephonically, by electronic mail messages, or by text messaging. The firewall must either send the alert to a management console that is actively monitored by authorized personnel or use a messaging capability to send the alert directly to designated personnel.